In molding a green tire, there has been conventionally conducted a method comprising the steps of: providing a cylindrical carcass band or green case on a shaping drum; bulging a center portion of the carcass band or green case into a toroidal shape; and uniting it to a belt/tread band established by bonding tire component members such as a belt member and a tread rubber separately on a belt/tread forming drum.
However, in such a conventional method, the belt/tread band is once detached from the belt/tread forming drum, gripped from radially outside, moved to the shaping drum, and this gripping is released there so as to move the belt/tread band onto the shaping drum, with the result that the steps are made complicated and the tread band is gripped and released many times, thereby causing a problem of a deteriorated accuracy of relative positions between the carcass band or green case and the belt/tread band. To deal with it, there has been proposed a method for directly assembling tire component members to a carcass band on a building drum, as disclosed in JP-2002-326288A.
The above proposal is capable of solving the complexity of steps. However, in assembling tire component members, side portions of a carcass band are once folded back to radial outsides around bead cores, respectively, a center portion of the toroidally bulged carcass band is then supported from a radial inside by a core device in a state where the bead cores are not locked to a building drum, and tire component members are assembled onto the core device. This fails to attain a relative positional relationship between the assembled tire component members and bead cores with high accuracy, thereby still failing to solve the above problem in this point.
The present invention has been conceived in view of such a problem, and it is therefore an object of the present invention to provide a tire building drum and a tire building method capable of assembling tire component members directly onto a building drum having a carcass band provided thereon and capable of assembling the tire component members with high precision, in molding a tire by folding back side portions of the carcass band to radial outsides around bead cores, respectively.